Specs For The Notch In The Colt Open Bolt Carrier

[A&S Conversions]

Hey guys, does anyone have the specifications for the notch in the bottom of the Colt open bolt carrier? I thought I had a line on one, but it fell through. I have all the fire control, but I don't have the carrier specifications. I understand that this system is very hard on the hammer pin. Any help would be greatly appreciated.

Scott

 

[A&S Conversions]

Update for those following along, I did find an original Colt open bolt carrier and purchased it. While it was very expensive, having one will not only give the physical specs of the notch but I can get the notch tested to get the heat treatment of of it. So after cutting the notch in a couple of standard carriers, I can get the the bottom of those carriers heat treated to the proper specs. That way the sear notch the hammer goes into will last.

Scott

 

[Concorde]

New project?

 

[A&S Conversions]

No, not a new project. The ATF said in their second determination that they didn't like that the Tenko was closed bolt and direct impingement rifle caliber instead of 9mm or .45 blowback of the original. We are making some modifications to make it more difficult to fire the Tenko without the M10 lower receiver. We also plan to adapt the Colt LMG open bolt mechanism to the Tenko. I think that it is an excepted fact that an open bolt pistol caliber system with a fixed firing pin is much more likely to have an out of battery detination than a striker or hammer fired system as the bolt must be in battery for the firing pin to hit the primer. We are trying to get the Tenko to pass. I want to give it the best chance possible. With the Colt open bolt carrier we will have the specs to modify a Colt style 9mm bolt to be used with the Tenko. Once we can get the mechanism to pass, then we will work on getting the other systems being passed.

Scott

 

[mattnh]

Hi Scott,
Glad to hear you located the part you needed!!!

 

[A&S Conversions]

Thank you. That is "the" difficult part to find and it was not cheap, but I have it.

Scott

 

[theduke]

I think the Nuge had some info on this...its been a few years and I recall asking about this topic...perhaps not your particular ? but along the same lines and for the same gun.

I like open Bolts...the way they should all be imo of course.

 

[A&S Conversions]

I like open Bolts...the way they should all be imo of course.

You are of course entitled to your opinion but the market and history would seem to disagree. It is my understanding that the Germans invented the concept of of the Assault Rifle (medium power select fire rifle used in the movement of troops. The MG43 was open bolt this was fine in auto, but made accuracy at distance challenging. The MG44 was closed bolt and was much more accurate at distance because the only movement of the gun was the fire control instead of the fire control and the bolt group of the open bolt MP43.

It is also my understanding that the only style of firearm that has been produced in the last 30 to 40 years with an open bolt mechanism is a light to heavy machinegun. I have heard of some Assault Rifles being produced with closed bolt function for semi and open bolt for auto. But it seems to me that most Assault Rifles are closed bolt operation. Most rifles are designed to be shouldered and would tend to be used for aimed fire. While a Light General Purpose Machineguns tend to be mounted and used for suppressive or indirect fire.

Since open bolt and closed bolt are two different mechanisms, the manual of Arms is different. All open bolt owners need to learn, if you have any problem, lock the bolt back. With closed bolt, most would tend to pull the mag first. Pulling the mag first with an open bolt will tend to get you an accidental discharge. Again, your guns, your choice. I would like to convert the two hosts for my DIAS that I have for my Valkyrie Armaments belt fed mechanism to open bolt.

Scott